Hot air furnace



March 22, 1966 H. c. LoHMAN HOT AIR FURNAGE Filed OCC. 25. 1963 i emv mk myc@ @H llll a Illlrllllrlu Il!!! INVENTOR.

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United States Patent O 3,241,544 HOT AER FURNACE Harry C. Lohman, La Crosse, Wis., assigner to The yfrane Company, La Crosse, Wis., a corporation of Wisconsin Filed st. 25, 1963, Ser. No. 318,871 14 Claims. (Cl. 126-116) This invention relates to fluid fuel red hot air furnaces, space heaters and the like. More particularly, this invention relates to a clamshell heat exchanger of novel construction having an integral draft diverter.

A principal object of my invention is to provide a fluid fuel fired air heater having a plurality of clamshell heat exchangers which may be modulated sectionally.

Another object of this invention is to provide a heat exchanger wherein no external draft diverter is required.

A further object of my invention is to provide a heat exchanger wherein `the walls of the draft diverter may function as heat exchange surfaces.

Still a further object of my invention is to provide a heating apparatus wherein the products of combustion are diluted and cooled prior to entering the flue gas manifold.

Other objects and advantages will `become apparent as this specification proceeds to describe the invention with reference to the accompanying drawings in which:

FIGURE l is a side elevation of a gas tired unit air heater or furnace having an upper portion of the casing side thereof broken away to show the upper portion of one of the clamshell heat exchangers thereof and having a portion of one shell of said clamshell heat exchanger broken away to show a combustion ilue gas restrictor and baffle means therein;

FIGURE 2 is a sectional view taken at line 2-2 of FIGURE 1 showing a rear end View of the heat exchanger clamshells as well as the fuel gas supply manifold with valve means for sectionally modulating the furnace;

FIGURE 3 is a view of a portion of the device taken at line 3 3 of FIGURE l;

FIGURE 4 is an elevational view of a portion of a modied form of a clamshell heat exchanger with integral draft diverter wherein the flue gas manifold is connected at the top adjacent the rear end thereof remote from the integral draft diverter air inlet;

FIGURE 5 is an elevational view of a portion of another modiiied form of a clamshell heat exchanger with integral draft diverter wherein the flue gas manifold is connected at the middle of the top edge thereof; and

FIGURE 6 is an elevational view of a portion of still another modified form of a clamshell heat exchanger with integral draft diverter wherein the ilue gas manifold is connected at the rear side of the exchanger remote from the integral draft diverter air inlet.

Each of the clamshell heat exchangers of FIGURES 4-6 are broken away as in FIGURE 1 to show the liuc gas restrictor and baille means therein.

Now referring to FIGURES 1-3, a gas fired hot air furnace 10 is shown as having a casing 12 of generally rectangular configuration having a front wall 14, a rear wall 16, a top wall 18, a bottom wall 20, and a pair of substantially parallel spaced sides 22. A motor driven propeller fan 24 is disposed in a circular air intake aperture 26 in rear wall 16 for blowing relatively cool air horizontally into casing 12.

Front wall 14 is provided with a rectangular hot air discharge aperture 28. A plurality of louvers 30 may be arranged in said discharge aperture to direct the flow of heated air from the furnace or heater casing.

Disposed within casing 18 in parallel relation with sides 22 are a plurality of spaced generally rectangular planar clamshell heat exchangers 32.

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Each of said clamshell heat exchangers 32 is comprised of two substantially allochiral concave-convex sheet metal shells arranged with their concave sides in face-to-face relation and welded or otherwise connected together along a peripheral flange 34 thereof.

The concave interior side contour of each shell is such as to provide a generally enlarged horizontally extending combustion chamber 36 at the base thereof which is in fluid communication with a somewhat narrower heat exchange chamber 38 having generally corrugated walls for eilicient heat transfer. Disposed within each combustion chamber 36 and extending through an aperture 4t) at the rear edge thereof is a ribbon type gas burner 42. Each gas burner is connected to a gas supply manifold 44 via a gas-air mixing means 46. Aperturas itl are in fluid communication with chamber 4S which is formed at the lower rear corner of casing 12. Partition 50 prevents the air blown by fan 24 from entering into apertures 40. Chamber 48 is provided with a rectangular combustion air inlet aperture 52 on the rear side thereof.

The concave interior side contour of each clamshell heat exchanger is such as to define an integral draft diverter passage 54 in the form of generally enlarged elongated horizontally extending cavity adjacent the top side thereof. The lower wall of the draftdiverter passage is in fluid communication with the upper portion of heat exchange chamber 38. The front end of passage S4 is open at 56 to the atmosphere to provide a draft diverter passage air inlet aperture for each clamshell. A vertical transversely extending bafe member 57 may be provided adjacent to apertures 56 having a plurality of apertures in registry with apertures 56 so that air blown by fan 24 will not draw gases outward through apertures 56. Each passage 54 is provided at the upper rear corner thereof with an upwardly and forwardly inclined ue gas discharge aperture 58 opening into an elongated transversely extending horizontal flue gas manifold 60 having a cross-section of generally triangular configuration formed by forwardly and upwardly inclined wall 62, upwardly and rearwardly inclined wall 64, and horizontal manifold top wall 66 which may be spac-ed from casing top wall 13 so the casing does not become excessively warm. Likewise, manifold 60 is provided with generally triangular end closing members 68 spaced fromsides 22 of casing 12. Manifold 60 may be connected to a ilue 7i) which ext-ends outward through casing top wall 18 and may be connected in any convenient manner to a flue stack (not shown).

Gas supply manifold 44 may be provided with several solenoid shut-off Valves 7.2, 74, and 76 to control the number of heat exchangers in operation. Thu-s, if valve 72 is closed, no fuel gas will be supplied to any of the burners. If valves 76 and 74 are closed and valve 72 open, gas will .be delivered to two of the six burners shown. If valves '7'4 and 72 are open and valve 76 closed, four of six heat exchangers will be placed in operation. And, if all valves are opened, all heat exchangers are placed in operation. The `operation of valves 72, 74, and 76 may `be automatic or manual. The ignition means (not shown) used for the burners may be of any convenient type, either automatic or manual, and does not constitute a part of the present invention.

Disposed within each clamshell heat exchanger between the draft diverter passage 54 and the heat exchange chamber 38 is a horizontally extending partition 78 which is provided with a plurality of dished louvers 80 which extend alternately upwardly and downwardly of the plane of the partition in a manner to direct gases leaving the heat exchange chamber 38 away from the Iapertures 58 toward apertures 56. While flue gas will normally discharge through apertures 58, any abnormal back iiow or restriction in the flue stach will cause the iiue gas to flow out apertures 56 thus preven-ting the burner ame from being extinguished. Louvers 80 progressively increase in size and spacing toward apertures 58. Partition 78 sealingly engages the inner wall of each shell of the clamshell heat exchanger so as to divert substantially all combusti-on gases passing from chamber 38 to passage 54 through apertures 78.

During the operation of my novel unit heater, hot combustion flue gas will rise within the clamshell from the combustion chamber thereof, through the heat exchange chamber, through apertures 78 into the draft diverter passage 54 where it mixes with cooler air normally drawn in through the draft diverter apertures 56. This mixture of gases fiows through aperture 58 into the fiue gas manifold 60. Manifold 60 collects the flue gas from the several clamshells which has been reduced in temperature from about 600 F. to 400 F. by mixture with draft diverter air and delivers the mixture to flue 70, where it may be exhausted to a stack means in any known manner.

During this operation cool air is blown by fan 24 over the outside surfaces of the clamshell heat exchangers including the outside walls of the heat exchange chamber portion 38 and the outside walls of draft diverter passage 54 and outward of the heater through aperture 28. As aforementioned, bale 57 prevents air blown by fan 24 from interfering with the flow of air normally entering apertures 56 which liow is essentially in the opposite direction.

Not only is it extremely economical to construct the draft diverter as an integral part of the two shells which form the clamshell exchanger, but such an arrangement permits the flue gas or exhaust gas manifold to operate at cooler temperatures. Since draft diverters also have the effect of regulating the fiow of air drawn through apertures 40 into 4the combustion chamber, a greater economy of operation may be achieved by the furnace or heater when it is sectionally modulated by closing valves 76 and/or 74 as the effective draf-t diverter area remains proportional to the number of clamshell heat exchangers operating.

In the modified form of clamshell heat exchanger shown in FIGURE 4 hot combustion gases from the heat exchange portion 138 are delivered to the draft diverter passage 154 having an opening to the atmosphere at 156. The draft diverter passage `i154 discharges cooled flue gas through an aperture 158 on the top side thereof adjacent the end remote from aperture 156 into a fiue gas manifold 160 arranged above aperture 158. Partition 178 with louvers 180 controllably restrict the fiow of iiue gas from the heat exchange chamber to the draft diverter passage.

In the modification shown in FIGURE 5, flue gas from heat exchange chamber 238 fiows through louvers 280 in partition 278 and enters the draft diverter passage 254 where it is mixed with air entering openings 256 at each end thereof. The cooled fiue gas egresses through aperture 258 at the center of the top thereof and is collected in flue gas manifold 260 mounted above aperture 258. Since two diverter apertures 256 are employed in this form, two sets of louvers 280 are also used to obtain proper control.

In the modification shown in FIGURE 6, the flue gases from heat exchange chamber 338 passing through louvers 380 in partition 378 enter diverter chamber 354 where they are cooled by mixing with air entering draft diverter aperture 356 and delivered through aperture 358 to a fiue gas manifold 360 at the rear side thereof. The heat exchange and combustion chambers of the clamshell forms of FIGURES 4-6 may be identical to those of the clamshell of FIGURES l-3.

The operation of the modified forms of clamshells shown in FIGURES 4-6 is similar to that of the form shown in FIGURES 1-3.

Although I have described in detail the preferred embodiment of my invention along with several other forms,

2. it is contemplated that many other changes may be made without departing from the scope or spirit of my invention and I desire to be limited only bythe Claims.

I claim:

1. A hot air furnace comprising a casing; a heat exchange means disposed in said casing; said hea-t exchange means including a plurality of clamshell heat exchangers; each of said clamshell heat exchangers cornprising a pair of sheet metal generally concave-convex shells arranved with their concave sides in face-to-face relation thereby generally defining a cavity therebetween, means sealingly connecting said shells along at least a portion of their peripheries, each of said shells including an area having an outwardly convex contour at t-he lower portion thereof emerging through the clamshell heat exchanger periphery thereby defining a combustion chamber and aperture therein for association with a fluid fuel burner, at least one of said shells of each pair further including an area at the upper portion thereof having an outwardly convex contour emerging through the clamshell heat exchanger periphery thereby defining a draft dive-rter passage with an air inlet aperture at said periphery, the area of said shells between said combustion chamber and said draft diverter passage defining heat exchange surfaces, and a discharge aperture in the periphery of each of said clamshell heat exchangers in fluid communication with said draft diverter passage and said combustion chamber for egress of combustion iiue gas and draft diverter air from each of said clamshell heat exchangers; means forming in said casing an air inlet aperture for receiving and passing air over the outside heat exchange surfaces of said heat exchange means; means forming an air discharge aperture in said casing for discharging air heated by said heat exchange means; and mean-s manifolding the discharge apertures of all of said clamshell heat exchangers.

2. The apparatus as defined in claim l further including a fluid fuel burner disposed in the combustion charnber of each of said clamshell heat exchangers and means for operating less than all of said burners for sectionally modulating said furnace.

3. The apparatus as defined in claim 1 wherein said draft diverter passage air inlet is disposed on the side of said clamshell heat exchanger adjacent said air discharge passage in said casing and wherein baffle means is provided to defiect air passing over said heat exchange surfaces from inducing fiuid flow from said draft diverter passage aperture.

4. A clamshell heat exchanger comprising a pair of sheet metal generally concave-convex substantially allochiral shells arranged with their concave sides in faceto-face relation thereby generally defining a cavity therebetween; means sealingly connecting said shells along at least a major portion of their peripheries, each or" said shells including an elongated area having an outwardly convex contour extending along the lower portion and emerging through the clamshell heat exchange periphery thereby defining a combustion chamber and aperture therein for receiving a Huid fuel burner; each of said shells further including an elongated area having an outwardly convex contour extending along the upper portion and emerging through the clamshell heat exchange periphery thereby defining a draft diverter passage with an air inlet aperture at the said periphery; the area of said shells between said combustion chamber and said draft diverter passage defining heat exchange surfaces; and means forming a discharge aperture in the periphery of said clamshell heat exchanger in fiuid communication with said draft diverter passage and said combustion chamber for egress of combustion flue gas and draft diverter air from said clamshell heat exchanger.

5. The apparatus as defined by claim 4 wherein a partition is arranged between said combustion chamber and said draft diverter passage, said partition being provided with flow restricting apertures having bafiie means associated therewith for defiecting fine gas from said combustion chamber toward said draft diverter passage inlet.

6. The apparatus as defined by claim 5 wherein the size of said fiow restricting apertures and bafile means increases progressively away from said draft diverter passage air inlet.

7. A heat exchanger clamshell for use in hot air furnaces and the like comprising a pair of generally rectangular concave-convex shells arranged with their concave sides in face-to-face relation thereby defining a cavity therebetween; the contour of at least one of said shells forming a first aperture in the lower portion of said clamshell for operative association with a fluid fuel burner for heating the interior of said clamshell; means defining a discharge aperture in the upper portion of said clamshell for discharging flue gas from said clamshell; and at least one of said shells being contoured to form a draft diverter passage means integral therewith along the top side thereof for preventing burner flame extinction by back draft.

8. A hot air furnace comprising in combination a plurality of clamshell heat exchangers disposed in sideby-side relationship, a plurality of draft diverters for preventing burner flame extinction by back draft each of which is operatively associated with one of said clamshell heat exchangers, and a liue gas manifold operatively associated with all of said clamshell heat exchangers.

9. A hot air furnace comprising in combination a plurality of clamshell heat exchangers disposed in sideby-side relationship, a plurality of draft diverters for preventing burner flame extinction by back draft each of which is operatively associated with one of said clamshell heat exchangers, and a fiue gas manifold operatively associated with all of said draft diverters.

10. A heat exchanger clamshell for use in hot air furnaces and the like comprising a pair of generally rectangular concave-convex shells arranged with their concave sides in face-to-face relation thereby defining a cavity therebetween; the contour of at least one of said Shells forming a first aperture in the lower portion of said clamshell for operative association with a fiuid fuel burner for heating the interior of said clamshell; means defining a discharge aperture in the upper portion of said clamshell for discharging fiue gas from said clamshell; and at least one of said shells being contoured to form a draft diverter passage means integral therewith along the top side thereof for preventing burner flame extinction by back draft, said draft diverter passage being provided with an air inlet aperture adjacent one end of said clamshell and said discharge aperture being disposed adjacent the end of said clamshell remote from said air inlet aperture.

11. The apparatus as delined in claim 10 wherein said discharge aperture is disposed on the top side of said clamshell.

12. The apparatus as defined in claim 10 wherein said discharge aperture is disposed on the vertical edge of said clamshell.

13. The apparatus as defined in claim 10 wherein said discharge aperture is disposed on the top side and vertical edge of said clamshell.

14. A heat exchanger clamshell for use in hot air furnaces and the like comprising a pair of generally rectangular concave-convex shells arranged with their concave sides in face-to-face relation thereby defining a cavity therebetween; the contour of at least one of said shells forming a first aperture in the lower portion of said clamshell for operative association with a fluid fuel burner for heating the interior of said clamshell; means defining a discharge aperture in the upper portion of `said clamshell for discharging flue gas from said clamshell; and at least one of said shells being contoured to form a draft diverter passage means integral therewith along the top side thereof; said draft diverter passage being provided with a pair of air inlet apertures, one being disposed at each end thereof and said discharge aperture for discharging flue gas being disposed intermediate said pair of inlet apertures.

References Cited by the Examiner UNITED STATES PATENTS 2,737,173 3/1956 Hauck et al. 126-110 2,923,287 2/1960 Murphy 126-307 X 3,058,457 10/1962 Fiedler 126--91 3,105,485 10/1963 Lucas 126-116 X JAMES W. WESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, JR., Examiner. 

1. A HOT AIR FURNACE COMPRISING A CASING; A HEAT EXCHANGE MEANS DISPOSED IN SAID CASING; SAID HEAT EXCHANGE MEANS INCLUDING A PLURALITY OF CLAMSHELL HEAT EXCHANGERS; EACH OF SAID CLAMSHELL HEAT EXCHANGERS COMPRISING A PAIR OF SHEET METAL GENERALLY CONCAVE-CONVEX SHELLS ARRANGED WITH THEIR CONCAVE SIDES IN FACE-TO-FACE RELATION THEREBY GENERALLY DEFINING A CAVITY THEREBETWEEN, MEANS SEALINGLY CONNECTING SAID SHELLS ALONG AT LEAST A PORTION OF THEIR PERIPHERIES, EACH OF SAID SHELLS, INCLUDING AN AREA HAVING AN OUTWARDLY CONVEX CONTOUR AT THE LOWER PORTION THEREOF EMERGING THROUGH THE CLAMSHELL HEAT EXCHANGER PERIPHERY THEREBY DEFINING A COMBUSTION CHAMBER AND APERTURE THEREIN FOR ASSOCIATION WITH A FLUID FUEL BURNER, AT LEAST ONE OF SAID SHELLS OF EACH PAIR FURTHER INCLUDING AN AREA AT THE UPPER PORTION THEREOF HAVING AN OUTWARDLY CONVEX CONTOUR EMERGING THROUGH THE CLAMSHELL HEAT EXCHANGER PERIPHERY THEREBY DEFINING A DRAFT DIVERTER PASSAGE WITH AN AIR INLET APERTURE AT SAID PERIPHERY, THE AREA OF SAID SHELLS BETWEEN SAID COMBUSTION CHAMBER AND SAID DRAFT DIVERTER PASSAGE DEFINING HEAT 